[Qt-interest] QAbstractSocket::waitForReadyRead() is not working

[Patric]

I have just searched and found that I have misunderstood the purpose of this 
method.
According to this thread 
http://www.qtcentre.org/forum/f-newbie-4/t-qudpsocket-binding-doesnt-work-19755.html

the bind method is just giving an inteface to my socket and the 
connectToHost is just making the need of specifing the peer address in the 
write function redundant.

----------------------------- quote
It all becomes clear once you understand how UDP works and how ::bind and 
::connect() work. UDP is connectionless protocol therefore with a single 
socket you can reach multiple targets and receive data from multiple 
sources. ::bind (and QUdpSocket::bind()) associates an address (interface 
and UDP port) with your (local) socket. Since this moment you can start 
receiving data on the socket because the operating system knows that if data 
reaches a specific UDP port on a specific network interface, it should be 
forwarded to your socket.

As UDP is a connectionless protocol it is obvious that ::connect() (and 
QAbstractSocket::connectToHost()) doesn't do any connecting. In particular 
no data gets exchanged in the network. All it does is that it associates 
your socket with a default remote address. Thanks to that you don't have to 
pass the peer address to functions for receiving or sending a datagram - 
instead the address you passed to ::connect() will be used. You can still 
receive datagrams from other addresses and you can still send datagrams to 
other addresses. The only difference is that you will have to specify peer 
addresses while sending or receiving if you don't call ::connect().
----------------------------- quote

But I don't understand two things here.
First, even if we use connectToHost to specify the peer address, we still 
have to call the writeDatagram method with IP Address and port.
And second, (this approach is used in the example of QUdpSocket), what means 
to bind without an Address, I mean to use
udpsocket.bind(162);
for example. From the documentation it is clear that in this case the 
QHostAddress::Any is used. But what means Any ? the purpose of bind is to 
give an interface to the socket, what will happen if we specify IP Address 
to Any ? Which is the default behaviour of the overloaded bind function, 
when only Port is passed.

Regards,
Patric



----- Original Message ----- 
From: "Thiago Macieira" <thiago.macieira at trolltech.com>
To: <qt-interest at trolltech.com>
Sent: Sunday, May 31, 2009 5:17 PM
Subject: Re: [Qt-interest] QAbstractSocket::waitForReadyRead() is not 
working


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